(1) Technical Field
This invention relates to a linear tape storage system represented by DLT (Digital Linear Tape) or LTO (Linear Tape Open) and, in particular, to a magnetic tape head actuator assembly (head transfer mechanism) for use in the system and a tape drive using the same.
(2) Prior Art
A linear tape storage system of the type has been developed as a backup for a computer system. A variety of linear tape storage systems have heretofore been proposed. For example, a digital linear tape drive as the DLT is disclosed in U.S. Pat. No. 5,862,014 or the like.
The digital linear tape drive (hereinafter may simply be called xe2x80x9cdriving devicexe2x80x9d, xe2x80x9ctape drivexe2x80x9d, or xe2x80x9cdrivexe2x80x9d) is adapted to receive a tape cartridge (hereinafter may simply be called xe2x80x9ccartridgexe2x80x9d) having a single reel (supply reel) and includes a take-up reel in the interior thereof. When the tape cartridge is loaded in the driving device, a magnetic tape is pulled out from the tape cartridge to be taken up by the take-up reel through a head guide assembly (HGA). The head guide assembly serves to guide to a magnetic head the magnetic tape (hereinafter may simply be called xe2x80x9ctapexe2x80x9d) pulled out from the tape cartridge. The magnetic head exchanges information between it and the tape. Typically, the head guide assembly comprises an aluminum plate having a boomerang-like shape and a plurality of large guide rollers, six in number, comprising bearings.
The head guide assembly is also called a tape guide assembly and is disclosed, for example, in U.S. Pat. No. 5,414,585. An example of the guide roller is disclosed in Japanese Unexamined Patent Publication No. 2000-100025.
As disclosed in U.S. Pat. No. 5,793,574 for example, a tape drive typically comprises a generally rectangular housing having a common base. The base has two spindle motors (reel motors). The first spindle motor (reel motor) has a spool (take-up reel) permanently mounted to the base and the spool is dimensioned to accept a magnetic tape streaming at a relatively high speed. The second spindle motor (reel motor) is adapted to receive a removable tape cartridge. The removable tape cartridge is manually or automatically inserted into the drive via a slot formed on a housing of the drive. When the tape cartridge is inserted into the slot, the cartridge is engaged with the second spindle motor (reel motor). Prior to rotation of the first and the second spindle motors (reel motors), the tape cartridge is connected to the permanently mounted spool (take-up reel) by means of a mechanical buckling mechanism. A number of rollers (guide rollers) positioned between the tape cartridge and the permanent spool guide the magnetic tape as it streams at a relatively high speed back and forth between the tape cartridge and the permanently mounted spool.
The digital linear tape drive of the above-mentioned structure requires a pulling device for pulling the tape from the supply reel to the take-up reel. Such pulling device is disclosed, for example, in International Publication No. WO86/07471. According to the publication, take-up leader means (first tape leader) is coupled to the take-up reel. To the tape on the supply reel, supply tape leader means (second tape leader) is fixed. The first tape leader has a tab formed at its one end. The second tape leader has a locking hole. The tab is engaged with the locking hole.
Furthermore, a mechanism for joining the first tape leader to the second tape leader is required. Such joining mechanism is disclosed, for example, in International Publication No. WO86/07295.
Japanese Unexamined Patent Publication No. 2000-100116 discloses xe2x80x9cStructure of Leader Tape Engaging Partxe2x80x9d capable of locking an end of a leader tape (second tape leader) to a tape end hooking part of the tape cartridge without requiring a tab protruding on a lateral side of the leader tape.
U.S. Pat. No. 5,857,634 discloses a lock system for preventing the rotation of the take-up reel of the tape drive when the tape cartridge is not inserted into the drive.
On the other hand, Japanese Unexamined Patent Publication No. 2000-149491 discloses an example of the tape cartridge to be received in the digital linear tape drive.
U.S. Pat. No. 6,241,171 discloses a xe2x80x9ctape drivexe2x80x9d in which a tape leader is urged from a tape cartridge to a take-up reel without using a buckling mechanism or a take-up leader.
The tape drive further comprises a magnetic tape head actuator assembly. The magnetic tape head actuator assembly is positioned between the take-up spool and the tape cartridge along a tape path defined by a plurality of rollers. In operation, the magnetic tape streams back and forth between the take-up spool and the tape cartridge, coming into close proximity to the magnetic head actuator assembly while streaming along the defined tape path. An example of the magnetic head actuator assembly is disclosed in U.S. Pat. No. 5,793,574 mentioned above.
An existing magnetic tape head actuator assembly comprises a tape head assembly and a head transfer mechanism. The tape head assembly comprises a magnetic head, a head holder to which the magnetic head is mounted, and a pair of flexible printed circuits (FPCs) for electrically connecting the magnetic head and an external circuit. To the head holder, the tape head assembly and the head transfer mechanism are coupled through screws.
On the other hand, the head transfer mechanism comprises a lead screw with a thread ridge having a rotation center axis O extending in a vertical direction, a generally I-shaped head lift which has a hollow center portion opened in a semicylindrical area and which serves to hold the tape head assembly and to move the tape head assembly up and down, a preload bushing arranged in the hollow opened portion of the head lift and having a thread groove engaged with the lead screw, a lead screw gear attached to a lower end of the lead screw and driven by another driving means for rotating the lead screw around the rotation center axis O, and a head guide coupled to the head lift and having a thread groove engaged with the lead screw. In cooperation with the preload bushing, the head guide moves the head lift in an extending direction (vertical direction) of the rotation center axis O in response to the rotation of the lead screw around the rotation center axis O.
The head lift has the above-mentioned hollow opened portion for receiving the preload bushing. The head guide is fixed to the head lift.
Between the preload bushing and the lower surface of an upper end portion of the head lift, a preload spring is located in a compressed state. The preload spring is a compression coil spring. By the preload spring, the preload bushing is continuously subjected to a downward pressing force along the rotation center axis O of the lead screw while the head lift is continuously subjected to an upward pressing force along the rotation center axis O of the lead screw. Also, the head guide is continuously subjected to the upward pressing force along the rotation center axis O of the lead screw because the head guide is attached to the head lift.
A combination of the preload bushing and the preload spring serves as a backlash preventing mechanism for preventing backlash of the actuator assembly.
Specifically, before assembling the actuator assembly, the thread groove of the preload bushing is offset by a half pitch with respect to the thread groove of the head guide. In this state, the lead screw is successively inserted into the head guide, the preload bushing, and a bearing. As described above, by the preload spring, the preload bushing and the head guide are subjected to the downward pressing force along the rotation center axis O of the lead screw and the upward pressing force along the rotation center axis O of the lead screw, respectively. Therefore, while the head lift is moved up and down along the rotation center axis O of the lead screw following the rotation of the lead screw in a clockwise or a counterclockwise direction, an upper surface of the thread groove of the preload bushing is continuously kept in frictional contact with an upper surface of the thread ridge of the lead screw while a lower surface of a thread groove of the head guide is continuously kept in frictional contact with a lower surface of the thread ridge of the lead screw. Thus, it is possible to prevent the backlash between the lead screw and the head lift during movement of the head lift following the rotation of the lead screw.
Because of little variation in elastic force of the preload bushing and the preload spring, it is possible to obtain a stable pressing force in an axial direction of the lead screw.
In the above-mentioned existing magnetic recording tape drive of a fixed-head type, backlash or play of the head lift for moving the head up and down is eliminated as mentioned above. Specifically, the compression spring presses the preload bushing with the thread groove so that thrust play between the head lift and the lead screw is eliminated.
In the existing structure, however, the play in the thrust direction can be absorbed but the play in the radial direction can not be sufficiently absorbed.
It is an object of this invention to provide a head transfer mechanism capable of absorbing play of a head assembly not only in a thrust direction but also in a radial direction.
It is another object of this invention to provide a head actuator assembly using the above-mentioned head transfer mechanism.
It is still another object of this invention to provide a tape drive comprising the above-mentioned actuator assembly.
According to an aspect of this invention, there is provided a head transfer mechanism for moving a head assembly up and down in an axial direction extending in a vertical direction, wherein the head transfer mechanism comprises a lead screw with a thread ridge having a rotation center axis extending in the axial direction, a head elevation guiding member including as an integral structure a head lift with the head assembly mounted thereon and a head guide having a thread groove engaged with the lead screw and serving to move the head lift up and down along the rotation center axis following the rotation of the lead screw, the head lift having a through hole receiving the lead screw inserted therethrough and a hollow opened portion formed at its center, a preload bushing arranged in the hollow opened portion of the head lift and having a thread groove engaged with the lead screw, and a compression coil spring arranged in the hollow opened portion of the head lift between the preload bushing and the head lift for applying the head lift with a pressing force in the axial direction of the lead screw, the head assembly being given a biasing load within the head elevation guiding member in a radial direction of the lead screw.
According to another aspect of this invention, there is provided an actuator assembly comprising the above-mentioned head transfer mechanism
According to still another aspect of this invention, there is provided a tape drive comprising the above-mentioned actuator assembly.